Laserfiche WebLink
<br />carefully filtered through 0.45 pm pore-size polycarbonate filters to <br />determine species composition and abundance of nannoplankton, defined as <br />plankton in the size range 0.45 to 25 pm. <br /> <br />Benthic macroinvertebrates. - Bottom samples for determining species <br />composition and abundance of benthic macroinvertebrates were collected with an <br />0.0232 m2 (15 x 15 cm) Ekman sampler and screened in a 600 ~m mesh littoral <br />bucket. Replicate samples were collected at each main river and backwater <br />site. Samples were preserved with sufficient buffered formalin to yield a <br />final concentration of 5-10 percent for subsequent laboratory identificaiton <br />and enumeration. Benthic organisms were sorted from the preserved samples, <br />identified to lowest practical taxon, and enumerated. Questionable taxa were <br />examined by personnel from the Larval Fish Laboratory, Colorado State <br />University, Fort Collins, Colorado. Undetermined chironomid larvae were <br />placed in the nearest genera or classified as unidentified. Dry weights of <br />identified organisms were determined after overnight drying in an oven at <br />90 .C, to determine dry weight biomass/m2. Benthic macroinvertebrates were <br />identified using Pennak (1978), Merritt and Cummins (1978), Simpson and Bode <br />(1980), Stewart and Loch (1973), Mason (1968) and Beck (1979). <br /> <br />Fish sampling and food habit studies. - Fish for food habit studies were <br />provided by the USFWS in 1987; in 1988, we collected fish using a 3/16-inch <br />(4.8 mm) mesh 10-foot-(3 m)-long seine, and a 1/16-inch (1.6 mm) larval seine. <br />qualitative seine hauls were made and a subsample of the fish preserved for <br />later analysis by the Larval Fish Laboratory (LFL), Colorado State University, <br />Fort Collins, Colorado. At the LFL, specimen and sample examinations were <br />performed under binocular dissecting or compound light microscopes fitted with <br /> <br />22 <br />